Several different factors have been suggested to be responsible for the well documented decline in immune function in both aged humans and experimental animals. A possible source of this immune dysfunction has been suggested to be due to abnormal levels of suppressor cells and/or suppressive soluble factors. Recently described procedures for quantifying soluble suppressor factors as well as the current stage of knowledge concerning suppressor cells allows the level of these immunosuppressive elements to be tested in aged individuals. The research proposed here asks the single question of whether or not suppressive elements play a role in the immune dysfunction of aging. Experiments to detect age related changes in suppressor cells and soluble factors are outlined.